1. Field of the Invention
The invention relates to a process for the treatment of turbid liquids, containing finely divided solids, with a granular treating agent which is placed in a fixed bed through which the turbid liquid flows. The invention especially relates to a process for the hydrolysis of the lactose in whey by means of a lactase immobilized on support particles. The support particles loaded with lactase are placed as a fixed bed in a predominantly tubular reactor. As a result, the substrate inhibition which would restrict the conversion of the lactose in a fluidized-bed catalyst is suppressed.
2. Description of the Prior Art
The continuous lactose hydrolysis of lactose by means of a lactase which is bound adsorptively to bead-shaped support particles has been described in DE-OS No. 28 39 737. The process can be performed continuously over several days only if a whey permeate is used from which the natural turbidity has been removed by ultrafiltration.
In the process according to DE-OS No. 31 22 231, the whey is acidified, heated and centrifuged to remove suspended materials. Nevertheless, daily cleansing of the enzyme catalyst is essential in this process, for even following centrifuging there still remain so many colloidally dissolved proreins in the whey that a coating precipitates on the support particles which impairs the activity of the immobilized lactase. For cleaning, the enzyme catalyst, which is placed on a fixed bed, is swirled and flushed with a protease solution that degrades the protein coating and reactivates the lactase.
This process is costly and uneconomical on account of the pretreatment of the whey by heating and centrifuging. However, if unclarifed whey with a turbidity of over 100 NTU is used in this process, then the fixed-bed packing of the enzyme catalyst is gradually transformed into a continuous plug that cannot be swirled and cleansed even by reversing the direction of flow. This phenomenon is primarily observed when the catalyst is frequently re-used.
Therefore, a need continues to exist for a process by which it is possible to continuously treat turbid liquids to convert the same without having to use the prior processing steps of heating and centrifuging. ln particular, a need continues to exist for a simple process which permits continuous hydrolysis of lactose in unfiltered whey and which ensures a long enzyme-catalyst life time.